The present invention relates generally to systems for controlled transmission of video and audio signals. More specifically, it relates to a unified system for controlled automatic selection and transmission of video and audio signals for use in mobile vehicles.
Systems for the electronic production of video signals or audio signals are known in the art. For example, video cassette recorders (VCR's) with their associated amplifiers, monitors and speaker systems convert images and sounds recorded on magnetic tape or optical disk to images and sounds perceivable by the human senses. Audio signals, such as RF signals or signals recorded on magnetic tape or optical disk, may be transformed into humanly perceivable sounds by radios, cassette tape players or optical disk players. Controls for such systems include selectors for one of several active channels, stations or programs, volume and tone controls, and advance/rewind controls.
Typically, such systems are stationary and operate on power provided by an AC power source. Audio systems have been adapted for use in airplanes to provide taped entertainment and information via headsets worn by passengers. Video entertainment, such as motion picture films, typically has been supplied on airplanes by well known projection machines displaying the visual image on a screen commonly viewed by numerous passengers. Public announcement systems have also been adapted to airplane use, as with the microphone and speaker systems used by airplane crew members.
Several devices have attempted to provide some degree of signal selection in audio systems. For example, U.S. Pat. No. 4,070,698 to Curtis et al. discloses an audio system in which one of several tracks of a multi-track tape player is selected for transmission. A timer control is provided for activating the tape player. The taped recordings include periodic commercial messages which are played while the background recording of music is caused to fade. Curtis et al. is designed to be used in commercial establishments, such as grocery stores, to allow automatic periodic recorded announcements without the need for an operator to interrupt the background music to make a live announcement. Curtis et al. does not provide for integration and automatic selection of multiple audio sources and video transmission, and does not teach or suggest the use of a low voltage, low current power supply.
Another device which attempts to provide some degree of audio signal selection is disclosed in U.S. Pat. No. 4,513,284 to Right. In Right, several control consoles are interconnected and are also connected to a plurality of remote stations. Each console is connected to a separate audio input and to the remote stations at which the audio signal is transformed into audible sounds. Each console has a hierarchical position relative to the other consoles, and when a console is activated, the consoles of a lower hierarchical position are disconnected from the remote station.
Right does not teach a single control for a plurality of audio signals, nor does Right teach or suggest the integration and automatic selection of video and audio signals. Moreover, Right teaches accomplishment of control of the audio output of the system simply by connecting and disconnecting the audio signals of selected consoles from the remote stations, rather than by the selection of a single audio signal by a unified central control to be transmitted to an audio output mechanism. Right also fails to teach or disclose any means for meeting changing output power requirements.
Another device which attempts to provide some degree of audio signal selection is described in U.S. Pat. No. 4,035,589 to Parke. In Parke, a single audio amplification and transmission device is provided for use in mass transit vehicles to provide background music and means for making public announcements. In this system, one audio signal is provided by a magnetic tape recording and playback device and another audio signal is provided by a microphone, as for public announcements. A time delay network in the system provides for the partial rewinding of the tape when the microphone is in use and for restart of the tape playback when the microphone is no longer in use.
Parke does not provide for the transmission of the audio signal of a video tape in addition to an audio tape recording signal and a microphone signal. Moreover, Parke does not provide for integration of a video signal with audio signals, nor does it provide for the automatic transmission of video and audio signals in accordance with a predetermined signal hierarchy. Parke also does not teach or suggest the use of a low voltage, low current power supply which would allow reduction of the size of the device. Parke also does not teach or disclose means to add additional power amplifiers to the system to meet changing output power requirements.
It can be seen that known systems do not provide a unified video and audio signal control and distribution system capable of automatically selecting one of a radio/tape audio signal, an audio signal associated with a video tape, and a public announcement system audio signal according to a predetermined signal selection hierarchy. Nor do such systems provide for the integration of a plurality of video monitors with an automatic signal selection means.
Another disadvantage of such systems is that they are not readily adaptable to mobile vehicle use, such as in a tour bus, in which compact size, ability to operate on low supply current, input sensitivity adjustment and variable output power capability are highly desirable features. Furthermore, use of such systems in mobile vehicles would require substantial operator training to ensure proper use, and would require that the operator of a vehicle physically operate the system while the vehicle is in motion, thereby presenting a safety hazard.